WDPN31 PGTW 191500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 19W (NINETEEN) WARNING NR 003// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL DEPRESSION (TD) 19W (NINETEEN), LOCATED APPROXIMATELY 356 NM EAST OF MANILA, PHILIPPINES, HAS TRACKED WESTWARD AT 12 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY DEPICTS A BROAD SYSTEM WITH CONVECTIVE BANDS SPIRALING INTO A PARTIALLY EXPOSED LOW LEVEL CIRCULATION CENTER. DEEP CONVECTION APPEARS TO BE LIMITED TO THE WESTERN HALF OF THE CIRCULATION, WITH THE BANDING FEATURES ON THE WEST SIDE BECOMING INCREASINGLY WELL ORGANIZED OVER THE PAST COUPLE OF HOURS, WHILE THE EASTERN HALF OF THE SYSTEM REMAINS RELATIVELY FREE OF DEEP CONVECTION AND THE SPIRAL BANDS ARE SOMEWHAT MORE ILL-DEFINED. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON ANALYSIS OF THE EXPOSED OUTER BANDS EVIDENT IN ANIMATED INFRARED IMAGERY. THE INITIAL INTENSITY OF 30 KNOTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON ANALYSIS OF MULTI-AGENCY DVORAK CURRENT INTENSITY ESTIMATES OF T2.0 (30 KNOTS) FROM PGTW, T2.5 (35 KNOTS) FROM KNES AND T1.5 (25 KNOTS) FROM RJTD, AS WELL AS AN ADVANCED DVORAK TECHNIQUE ESTIMATE OF T2.3 (32 KNOTS). TD 19W CONTINUES TO TRACK ALONG THE SOUTHERN PERIPHERY OF A SUBTROPICAL RIDGE EXTENDING SOUTHWESTWARD FROM A CENTER NEAR 30N 155E TO NORTHERN VIETNAM. THE SYSTEM IS TRACKING THROUGH A GENERALLY FAVORABLE ENVIRONMENT WITH WARM SSTS (29-30 DEG CELSIUS), LOW (10-15 KNOTS) VWS AND MODERATE UPPER- LEVEL OUTFLOW ON THE DIVERGENT SOUTHWEST QUADRANT OF AN UPPER LEVEL ANTICYCLONE. 3. FORECAST REASONING. A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TD 19W WILL TRACK WEST-NORTHWESTWARD THROUGH TAU 72 UNDER THE STEERING INFLUENCE OF THE DEEP-LAYER STR TO THE NORTH. THE SYSTEM IS EXPECTED TO MAKE LANDFALL ALONG THE EAST COAST OF CENTRAL LUZON SHORTLY AFTER TAU 24, THEN REEMERGE INTO THE SOUTH CHINA SEA BY TAU 36. WHILE A WEAKNESS IS STILL EXPECTED TO DEVELOP IN THE STEERING RIDGE AROUND TAU 48, THE VAST MAJORITY OF THE MODEL GUIDANCE INDICATES THAT THE MAIN IMPACT ON THE TRACK OF TD 19W WILL BE TO SLOW ITS FORWARD SPEED, WITH ONLY A VERY SMALL JOG TO A MORE NORTHWESTWARD TRACK BETWEEN TAUS 48 AND 72. THE SYSTEM IS CURRENTLY EXPERIENCING A BIT OF EASTERLY SHEAR, PUSHING THE MAJORITY OF THE CONVECTION OFF TO THE WEST OF THE CENTER, AND THIS PATTERN IS EXPECTED TO CONTINUE THROUGH TAU 72, ALLOWING FOR ONLY SLOW BUT STEADY INTENSIFICATION. AFTER MAKING LANDFALL ON LUZON, THE SYSTEM MAY WEAKEN SLIGHTLY BUT ONCE BACK OVER WATER WILL QUICKLY REGAIN INTENSITY AND THEREAFTER RESUME SLOW BUT STEADY INTENSIFICATION, REACHING A PEAK OF 55 KNOTS BY TAU 72. NUMERICAL TRACK GUIDANCE HAS COME INTO MUCH BETTER AGREEMENT SINCE THE PREVIOUS RUN, WITH ALL CONSENSUS MEMBERS WITHIN THE EXCEPTION OF NAVGEM AND THE UKMET ENSEMBLE FORMING A VERY TIGHT ENVELOPE WITH LESS THAN 60 NM AT TAU 72. HOWEVER THIS SPREAD INCREASES TO 195 NM IF THE NAVGEM IS INCLUDED. THE ALTERNATE SCENARIO OF A MORE NORTHWARD TRACK INTO THE STR WEAKNESS IS STILL A POSSIBILITY, IF AN INCREASINGLY LESS LIKELY ONE, WITH ONLY THE TWO PREVIOUSLY MENTIONED MODELS SUPPORTING THAT SCENARIO AND EVEN THE HWRF NOW SIGNIFICANTLY CHANGING AND COMING IN LINE WITH THE REMAINDER OF THE TRACKERS. THE JTWC TRACK LIES JUST SOUTH OF THE MULTI-MODEL CONSENSUS TRACK THROUGH TAU 72 WITH HIGH CONFIDENCE. C. IN THE EXTENDED FORECAST, TD 19W IS EXPECTED TO TRACK WESTWARD THROUGH TAU 120 UNDER THE STEERING INFLUENCE OF A REFORMED AND STRENGTHENED STR IN THE NORTHERN SOUTH CHINA SEA. AS THE SYSTEM MOVES WEST IT WILL INCREASINGLY COME UNDER CONFLUENT UPPER-LEVEL FLOW, CHOKING OFF THE OUTFLOW, WHICH COMBINED WITH INCREASING VWS WILL LEAD TO A SLOW WEAKENING TREND THROUGH TAU 120. NUMERICAL GUIDANCE IS IN GOOD AGREEMENT WITH THE EXCEPTION OF NAVGEM, WITH ONLY A 65 NM SPREAD AT TAU 120 IF NAVGEM IS DISCOUNTED, AND 190 NM IF IT IS INCLUDED. THE JTWC FORECAST LIES TO THE SOUTH OF THE MULTI-MODEL CONSENSUS WITH FAIR CONFIDENCE IN LIGHT OF THE ALTERNATE SCENARIO AS REPRESENTED BY THE NAVGEM TRACKER.// NNNN